“Oregon’s rapid population and economic growth between 1985 and
2000 led to proposals for new freeways to meet traffic demands and reduce congestion.
Proposed projects included the Mount Hood Parkway, the Sunrise Corridor and
the Western Bypass in the Portland area and the West Eugene Parkway in Eugene.
For a variety of reasons including funding constraints, environmental concerns
and citizen opposition, none of the projects was constructed.”
– Atlas of Oregon, p. 104
www.cfst.org/articles/STIP_Sunrise_Comments.html and www.cfst.org/articles/TopTenReasonsNotSunriseFreeway.html

Mt. Hood Parkway was a proposed connection between I-84
and US 26. The Sunrise Freeway is a proposed expressway from Clackamas (I-205)
to Boring (US 26) outside the Portland UGB (it is still being pushed as a
core part of the recent UGB expansion around Damascus). The Western Bypass
would have run from I-5 south of I-205 to the Columbia River, where it would
have connected to I-5 north of Vancouver, WA. These roads would have been
parts of a de facto Portland Outer Beltway.

Myth: Oregon's planning laws hinder development of highways and other large
public facilities.
Reality: From 1979 to 1988, Oregon's Highway Division successfully completed
146 major transportation projects. Since Oregon's planning program began (in
1973), only two large project proposals have failed: the Mt. Hood Freeway (east
of Portland) and the Roosevelt Freeway (in Eugene). A 1988 study by a multi-agency
committee found “the overall record of siting public facilities in Oregon
to be good – probably much better than that found in other states.”http://www.uoregon.edu/~pppm/landuse/myths.html
Department of Land Conservation and Development DLCD, 1992

Thank you, neighborhood activists
People can drive past on Division or Clinton streets every day and never know
it’s there. Indeed, it wouldn’t be there at all, if supporters
of the Mount Hood Freeway had had their way.
The diminutive Piccolo Park (Southeast 28th Avenue between Division and Clinton
streets, 503-823-7529) cuts a grassy swath through a residential block. The
land was acquired by the state in the 1970s for a freeway, which would have
roared through this historic neighborhood, but the freeway planning faltered
and in 1989 the parcel was turned into a charming city park.
Piccolo means “small” in Italian, and Piccolo is a kid-size park,
with plenty of slides, swings, bridges and other things to climb on and race
around.
— AMD

This map from the Portland Planning Division's 1966 development plan illustrates
Robert Moses' vision for a city girdled by freeways. Red indicates existing
freeways; green indicates freeways that were never built.

I-505 (cancelled) Oregon
Unbuilt 1.44-mile Portland spur [1]; I-505 would have followed US 30 (Yeon Ave).
northwest out of Portland. Plans for this freeway were withdrawn in the late
1970s, culminating with an approval by President Jimmy Carter to cancel it on
Dec. 14, 1979. [11]The money was used for other construction projects in the Portland area,
including an alternate design for I-505. (The source doesn't elaborate
on this.) [11]
Part of the proposed route appears on a 1979 Gousha Portland city map. I-505
would have ended at I-405 at the Exit 3 ramps.
A 1970 proposal estimated the road at 0.7 miles and $3 million. [8] A 1972 report
has this summary:

The statement concerns the proposed construction of an urban freeway (Interstate
505) extending from a junction with Interstate 405 westerly to a junction
with St. Helens Road (US 30) in Northwest Portland, Multnomah County, Oregon.
The adverse environmental impacts include a general increase in land values
in Northwest Portland, the relocation of individuals and commercial/industrial
entities, changes in location and degree of noise levels, increased traffic
density within the freeway corridor.

I-305 (cancelled) Oregon
This is the proposed but unbuilt Salem Spur, intended to connect I-5 to city
streets in North Salem. I-305 would have followed the Salem Parkway (now Business
Route 99E). Its official length in the federal highway log was 3.3 miles. [4]
In 1977, I-305 was withdrawn from the Interstate highway system. Funds
were traded in for road projects in the area, including widening of the major
bridge across the Willamette River to West Salem. [7]
I-305 still appeared in some later road atlases, including the 1985 nationwide
edition by Rand McNally.
See also: Interstate 305 (Cancelled) (Mike Wiley)